In an interview with Talking Points Memo, Barbara Morgan, spokeswoman for New York City mayoral candidate Anthony Weiner, called former Weiner intern Olivia Nuzzi all sorts of names after Nuzzi publicly criticized the campaign. While the New York Times only revealed that Morgan used "several vulgar and sexist terms," the TPM report spelled it out: Morgan called Nuzzi a "bitch," a "cunt," a "twat," and most colorfully, a "fucking slutbag."
On Twitter, slutbag quickly achieved meme status, and Nuzzi even edited her Twitter profile to include it. Slang lexicographer Jonathon Green thanked Nuzzi for "inspiring some excellent citations." His magnum opus, Green's Dictionary of Slang, does not include slutbag, but it does illuminate how the derogatory term was formed in the first place. GDoS has an entry for -bag as a combining form:
-bag sfx [SE bag/BAG n.1 (1f); the implication is of being a receptacle for something, most usu. sperm; note also BAG n.1 (3)/BAG n.1 (5)] a sfx used in comb. with another term, usu. a n., to describe a contemptible, despised person; when of a woman, often with implications of promiscuity; see cits. at DIRTBAG n.; FUCKBAG under FUCK n.; GAB-BAG under GAB v.; HORNBAG under HORN n.2; JITBAG under JIT n.3; PISS-BAG under PISS n.; SCRUFF-BAG under SCRUFF n.; SLEAZEBAG under SLEAZE n.
The many cross-references in the entry indicate that the pejorative punch of -bag derives from multiple sources. Two additional -bag epithets to consider are scumbag and douchebag. Scumbag, as Jesse Sheidlower detailed for Slate here, originally meant "condom" (with scum meaning "semen") before it became so devulgarized that it can even appear in the New York Times crossword puzzle. Douchebag, as Jonathan Lighter's Historical Dictionary of American Slang informs us, has meant "a stupid, contemptible, or despicable person" (referring to a woman in its earliest sense) since the 1940s. (Standalone douche, minus the -bag, is an epithet of more recent vintage — see Brian Palmer's Slate Explainer.)
To these various X-bags we can also add hose-bag and ho-bag, which are both in the Oxford English Dictionary's online edition:
Etymology: < hose n. + bag n.
U.S. slang (derogatory).
A sexually promiscuous woman.
1974 R. L. Hill Nails xi. 123 You never worry about fuck-all anyway,..as long as you have your finger up some three-dollar hosebag.
1979 UNC-CH Slang (Univ. N. Carolina, Chapel Hill) (typescript) Mar. 4 She's a hosebag—I heard about her behavior with Tom, and then Jack, at the same party!
1995 H. Stern Miss Amer. (1996) i. 20, I just wasted an hour seducing this hosebag and she has a fucking headache?
2002 J. Grisham Summons (2003) vii. 61 What about that hosebag who ditched you? What's her name?.. Yeah, Vicki. I hated that bitch even at your wedding.
Etymology: < ho n.6 + bag n., perhaps after hosebag n.
N. Amer. slang (derogatory).
A sexually promiscuous woman; = hosebag n.
1989 Post-Standard (Syracuse, N.Y.) 15 Feb. b1/4 If it's a girl, you might call her a ho or ho bag. It stems from whore, but don't get too literal.
1994 Jrnl. Higher Educ. 75 92 A few college slang terms exist for women who are sexually inactive;..a great many epithets for women who are considered promiscuous, most of which are pejorative and subcultural terms (flinger, hose monster,..ho-bag, nympho).
2001 M. McCafferty Sloppy Firsts 10 Manda thinks that reading feminist manifestos makes up for her borderline ho-bag behavior.
2004 Toronto Star (Nexis) 23 Mar. c2, I was still a virgin. Regardless, as far as the gossips at my school were concerned, I was a ho-bag.
The latter term has, in fact, entered the Weiner/Morgan/Nuzzi story in a tangential manner — David Roberts, a blogger on energy politics for Grist, called Nuzzi a "hobag" in a tweet but later apologized.
NSFW Corp, the online magazine where Nuzzi originally criticized the Weiner campaign (before taking to the pages of the New York Daily News), has been having a lot of fun with slutbag and its potential meanings — catch Paul Carr's podcast here. But it should be noted that slutbag (or slut bag) has been around for a while, even if it hasn't made the slang dictionaries yet. In his 1987 novel Little Red Rooster, Greg Matthews included a rant about a "two-faced slut bag."